Nanobiosensors - Biosensors and Biosensor Kinetics - page 103

continuous oxidation of the reactive intermediates formed at the electrode surface. This was
clearly demonstrated, according to the authors, by the addition of glucose twenty times in a
row. In contrast, there was a 50% reduction in the current signal when the nickel bulk elec-
trode was used under similar circumstances.
The authors conclude that their NiCFP electrode has significant advantages that include good
analytical performance as well as a simple preparation process. It also demonstrates impor-
tant biosensor parameters, namely high sensitivity, a fast amperometric response, a low
detection limit, a wide linear range, and good resistance to surface fouling, leading to better
operational stability. Therefore they claim that their biosensor exhibits good potential as a
platform for mass production at low cost.
5.5 Use of Gold Nanoparticles in a Sensitive Immunochromatographic
Assay for the Detection of PSA in Serum ( Nagatani et al., 2006 )
Nagatani et al. (2006) have developed a sensitive immunochromatographic assay for
detecting PSA in serum. PSA was first identified by Hava et al. (1969) . Nagatani et al.
(2006) report that PSA is a 33 kDa intracellular glycoprotein that is formed only in the pros-
tate gland. PSA in serum exists both in the complex form (to a 1 -chymotrypsin; PSA-ACT)
and in free soluble form (f-PSA) ( Lilija et al., 1991; Zhang et al., 1999; Balk et al., 2003 ).
The authors claim that PSA in serum is a reliable marker for the early detection of prostate
cancer. Clinicians suggest that levels greater than 4 ng/ml are an indicator of a potential pros-
tatic abnormality ( Caplan and Kratz, 2002; Balk et al., 2003 ). Rather than total PSA (t-PSA),
the ratio of free PSA (f-PSA) to t-PSA is a better indicator of prostate cancer ( Prestigiacomo
and Stamey, 1995; Aslan et al., 2003 ; McArdle et al., 2004). They point out that both ELISA
(enzyme-linked immunsorbent assay) and CLEIA (chemiluminescent enzyme immunoassay)
have been routinely used to detect PSA, but that there is still a need to develop a portable and
low-cost device to detect PSA.
Nagatani et al. (2006) explain that an immunosorbent membrane strip is a unique low-cost
analytical device to detect analytes of interest, for example, in pregnancy diagnosis ( Bhaskar
et al., 1996; Chiao et al., 2004; Sato et al., 2004; Xiulan et al., 2005 ). Tanaka et al. (2006)
have recently used gold nanoparticles in the test line of a chromatographic strip. They claim
that this is a novel method to enhance the detection technique. They have used their novel
immunochromatographic adsorbent strip to detect PSA in serum. They point out that their
immunosorbent immunochromatographic strip uses less antibody in their test line than a nor-
mal immunochromatographic test strip and CLEIA. The antibody is an expensive component
of the detection device, and their method facilitates a lower cost.
They also declare that the procedure to develop their sensitive immunochromatographic test
strip for using less antibody is simple compared to the conventional procedure. They report